The objective on this work is the total synthesis of the novel ansa macrolide maytansin, an exceptionally interesting antitumor agent, which shows inhibitory activity against several murine tumors at the level of micrograms per kg body weight, and is a highly active inhibitor of cell division and of transformation of mouse cell cultures infected with murine sarcoma virus. Because of the scarcity of this material and the high cost of production from natural sources it is imperative to study the total synthesis of the natural products and of simpler structures showing the desired biological activity. It is expected that, as clinical trials with this compound progress, the search for substances exhibiting lower toxicity will emerge as a major objective. It is our feeling that the presence of the chloro and methoxy substituents in the aromatic ring are mainly of decorative value and as a first approach the synthesis of des-chloro des-methoxy maytansin is outlined. Particular attention is being paid to the stereo and regiospecificity of the reactions employed. Moreover, the synthesis of optically active materials of natural, enantiomeric and diastereomeric chiralities is possible on the basis of our synthetic plan. Suitable intermediates will be submitted to the NCI for assay in the KB cell culture and the P388 mouse leukemia screens.